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I-BAR domain
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What is an I-BAR domain?

Also known as IMDs (IRSp53-MIM homology domains), I-BAR domains bind to membranes and are distant relatives to the "classical BARs." They also homo-dimerise into the I-BAR module (see structure above). Notably, the I-BAR module of IRSp53-MIM is relatively flat. Membrane binding occurs on the bottom surface of the above structure (see comparison of the curvatures of membrane binding surfaces below) and thus the I-BAR module binds and stabilises negative curvatures.

Membrane deformation: When bound to liposomes I-BAR modules stabilize 78nm tubules that penetrate into liposomes (see Mattila et al 2007, and electron tomogram of tubulation, taken from this paper, shown below).
Other papers on the I-BAR module: (Yamagishi et al 2005, recognition of the IMD as a domain), (Millard et al 2005, structure of IRSp53 IMD), (Suetsugu et al 2006, showing surface protrusions on cell),(Lee et al 2007, structure of MIM IMD)

What is the function of an I-BAR module? IRSp53 is implicated in forming filopodial protrusions at the plasma membrane. It is thought that this is accomplished with the help of the I-BAR, which can localize the entire protein to the membrane and help induce/stabilize the negative curvature for filopodial formation.
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